// tspcluster - Traveling Salesman Problem
// Copyright (C) 2006  Frederik Carlier
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

using System;
using System.Collections.Generic;
using System.Text;

namespace UGent.Tsp
{
    /// <summary>
    /// Exposes methods to calculate distances.
    /// </summary>
    static class Distance
    {
        /// <summary>
        /// Calculates the distance between to given points using the metric specified.
        /// </summary>
        /// <param name="metric">The <see cref="Metric"/> to use.</param>
        /// <param name="dimension">The dimension of the space in which the metric is defined.</param>
        /// <param name="x">The coordinates of the first point.</param>
        /// <param name="y">The coordinates of the second point.</param>
        /// <returns>The distance between <paramref name="x"/> and <paramref name="y"/>, 
        /// using the metric specified.</returns>
        public static double Calculate(Metric metric, int dimension, double[] x, double[] y)
        {
            if (dimension < 0)
                throw new ArgumentOutOfRangeException("dimension");

            if (x == null)
                throw new ArgumentNullException("x");

            if (y == null)
                throw new ArgumentNullException("y");

            if (x.Length != dimension)
                throw new ArgumentOutOfRangeException("x");

            if (y.Length != dimension)
                throw new ArgumentOutOfRangeException("y");

            double distance = 0;

            switch (metric)
            {
                case Metric.Euclidian:
                    for (int i = 0; i < dimension; i++)
                        distance += Math.Pow(x[i] - y[i], 2.0);

                    distance = Math.Sqrt(distance);
                    break;
                default:
                    throw new MetricNotSupportedException(metric);
            }

            return distance;
        }
    }
}
